Two speed system for EEG recording

Abstract

A method and system for recording EEG waveforms whereby the amplitude of the waveform signal in both positive and negative direction is compared with variable levels and a trigger signal produced when the amplitude exceeds a level to cause the strip of recording paper to speed up for at least a predetermined time and to continue for the length of the seizure so that little paper is accumulated during periods of uninteresting activity while a complete readable record is produced of any notable EEG activity, such as an epileptic seizure.

What is claimed is: 
     
       1. A system for recording EEG electrical body waveforms comprising: means for detecting an EEG waveform and producing an electrical signal representing said waveform,   means for comparing the amplitude of said electrical signal with a predetermined amplitude level and producing a trigger signal when said amplitude of said electrical signal exceeds said predetermined level,   means responsive to said electrical signal for producing a graphical representation of said waveform on a strip of recording material,   means for driving said strip of recording material past said representation producing means, and   means for causing said driving means to change the speed at which said recording material is driven from a first speed to a second speed higher than said first speed when said comparing and producing means produces said trigger signal.   
     
     
       2. A system as in claim 1 wherein said representation producing means is a polygraph. 
     
     
       3. A system as in claim 1 wherein said causing means includes means for maintaining said second speed for a predetermined time following said trigger signal. 
     
     
       4. A system as in claim 1 wherein said causing means includes a one-shot flip-flop means connected to said comparing means for shifting from a first to second electrical condition at an output upon receipt of said trigger signal for a predetermined time and relay means connected to said flip-flop means for applying a first voltage signal to said driving means when said flip-flop means is in said first condition and a second voltage signal to said driving means when said flip-flop means is in said second condition. 
     
     
       5. A system as in claim 4 further including means for varying said predetermined time. 
     
     
       6. A system as in claim 5 wherein said predetermined time is roughly 4 seconds. 
     
     
       7. A system as in claim 4 further including indicator means connected to said flip-flop means output for indicating when said flip-flop means is in said second condition and accordingly said driving means is driving said strip at said second speed. 
     
     
       8. A system as in claim 1 wherein said comparing and producing means includes means for establishing said amplitude level and an operational amplifier with one input connected to said detecting means for receiving said electrical signal and the othe input connected to said establishing means for receiving said amplitude level. 
     
     
       9. A system as in claim 8 wherein said establishing means includes a variable resistor connected to said other input and a voltage source connected to said variable resistor for applying a D.C. voltage to said other input. 
     
     
       10. A system as in claim 9 wherein said comparing means and producing means includes means for establishing a second amplitude level having a polarity opposite the first amplitude level and a second operational amplifier with one input connected to said detecting means for receiving said electrical signal and the other input connected to said second amplitude level establishing means for receiving said second amplitude level having a polarity opposite the first amplitude level. 
     
     
       11. A system as in claim 10 wherein said second amplitude level establishing means includes a second voltage source, and second variable resistor connected to said other input of said second amplifier and to said second voltage source, said second voltage source having a polarity opposite that of the voltage source connected to the first variable resistor, for applying a second D.C. voltage thereto. 
     
     
       12. A system as in claim 11 further including first switch means for connecting and disconnecting said first variable resistor from said other input of said first operational amplifier and second switch means for connecting and disconnecting said second variable resistor from said other input of said second operational amplifier. 
     
     
       13. A system as in claim 1 further including means for amplifying said electrical signal from the detecting means, and   a high pass filter connected between said amplifying means and said comparing and producing means.   
     
     
       14. A system as in claim 1 wherein said strip is paper and said driving means includes a variable speed motor. 
     
     
       15. A system for recording EEG electrical body waveforms comprising: means for detecting an EEG signal and producing an electrical waveform signal,   means connected to said detecting and producing means for producing a trigger signal when the amplitude of said waveform signal in at least one polarity exceeds a predetermined level with respect to a given reference,   means responsive to said waveform signal for producing a graphical representation of said waveform on a strip of recording material,   means for driving said strip past said representation producing means, and   means for changing the speed at driving said strip for a predetermined time from a first speed to a second speed higher than said first speed upon production of said trigger signal.   
     
     
       16. A system as in claim 15 wherein said trigger signal means includes means for establishing a positive predetermined level and a negative predetermined level above and below, respectively, a reference level, and means for comparing the amplitude of said waveform signal with said positive and negative levels and producing said trigger signal when said amplitude of said waveform signal exceeds one of said positive and negative levels.